The invention relates to a rack system having a mounting rack with slots for the insertion of electrical printed circuit board assemblies using centering and contact elements.
The mounting rack in such a rack system provides volume elements for the insertion of the electrical printed circuit board assemblies. These volume elements are also referred to as slots and are, in general, arranged lying and parallel next to one another. Electrical printed circuit board assemblies can then be inserted into these slots. Thereafter, the electrical printed circuit board assemblies lie parallel next to one another, too.
By way of example, FIG. 1, in addition to including certain inventive features discussed below, shows a standard, basic configuration of a mounting rack 50. The space for accommodating the printed circuit board assemblies is bounded by transverse connecting rails, which are arranged on opposite sides and composed of electrically conductive material. In the example of FIG. 1, there are two lower transverse connecting rails 36,37, and two opposite, upper transverse connecting rails 38,39. The transverse connecting rails 36,38 bound the front side of the mounting rack 50, i.e., the insertion side 35 for inserting the electrical printed circuit board assemblies. The two transverse connecting rails 37,39 bound the rear side of the mounting rack 50, which can be closed, for example, by a backplane.
The transverse connecting rails 36,37,38,39 can be mounted at the sides of a cubicle, for example inside the cubicle. The embodiment in FIG. 1 has vertical sidewall plates 40,41, to which the transverse connecting rails are laterally screwed. Finally, the top and the bottom of the mounting rack 50 are closed by respective upper and lower covering plates 47,48. Front elements are provided to close the insertion side 35 of the mounting rack 50. These front elements are assigned to the individual slots inside the mounting rack and are adapted to their widths. Furthermore, the front elements can be plugged on and pulled off. This closure capability is independent of whether or not the slot located behind a front element is occupied by an electrical printed circuit board assembly. Thus, on the one hand, empty slots can be closed by a front element that is slid onto the insertion side 35 of the mounting rack 50, much like in the manner of an empty spot closure. On the other hand, the electrical printed circuit board assemblies can be provided with a front element along one edge, so that, once the assemblies are inserted into the mounting rack 50, the front element covers the corresponding slot at the insertion side 35.
The example of FIG. 1 has front elements 52,8 for two slots 44,45, which are located on the left-hand side of the mounting rack 50. By way of example, the front elements include multiple parts. For instance, the front element 8 includes a vertical front panel 9, which is composed of electrically conductive material. Each of the upper and lower faces of the front element 8 includes an end part 10,1 which, as a rule, is likewise composed of an electrically conductive material. By way of example, lever handles 12,2 are rotatably borne at these end parts. These lever handles can be operated by one person, in particular by pivoting movements, so that at least the front element 8 can be inserted and withdrawn in a simple manner.
In the example of FIG. 1, the front element 52 is completely slid onto the slot 44 located behind the front element 52. The front element 52 covers the slot 44 and lies in the plane of the insertion side 35 of the mounting rack 50. By way of example, the front element 8 of the adjacently located slot 45 is firmly connected to a printed circuit board assembly 51. The connection is advantageously made with the aid of both end parts 10,1. For the most part, the printed circuit board assembly has been inserted into the slot 45. After the complete insertion of the assembly into the slot 45, the front element 8 is justified next to the front element 52 and lies in the plane of the insertion side 35, too.
During insertion of the front elements or units, which include the front elements and the electrical printed circuit board assemblies, these elements must be centered in the insertion direction, in particular immediately before they reach the completely inserted state. This avoids an accidental lateral offset, in particular, of the front elements, which would impede the complete insertion of the front elements or, in some circumstances, even prevent such insertion. This centering process is particularly necessary when adjacent slots are already covered by front elements at the insertion side. Therein, while centered as accurately as possible, the front element to be inserted must be moved forward onto the free opening of the respective slot. Furthermore, after the complete insertion of the front elements, the front elements must be secured against becoming detached, in particular if the front element is firmly connected to the electrical printed circuit board assembly located inside the slot. Finally, the front elements must make a reliable electrically conductive contact with the mounting rack, in particular if the front elements and their parts are largely composed of electrically conductive materials. Preferably, the front elements contact the transverse connecting rails of the mounting rack. This results in the front elements being connected to the protective-ground contact of the mounting rack. Therefore, even high fault currents can be dissipated from the front elements to the mounting rack. This makes it possible to trigger mains protection devices, such as load-break disconnectors or residual current devices, at a speed that ensures that personnel are protected.
Various designs are already known for centering and securing a front element.
For instance, European Patent EP 0 579 859 B1 discloses a printed circuit board assembly having guide pins to accurately insert a printed circuit board assembly into a mounting rack. Two guide pins for centering are provided on the outsides of the comer mounting bodies of the printed circuit board assembly. During insertion, the guide pins are supported on the side flanks of the opposite head end of a longitudinal guide rail. In addition, a ground contact pin is arranged between the guide pins. When the printed circuit board assembly is inserted, the ground contact pin enters a coding chamber at the end face of the opposite head end of the longitudinal guide rail. The coding chamber is occupied by a ground contact spring.
Finally, the comer mounting body has a mounting hole for receiving a screw. This screw can be connected to holding means in order to secure the printed circuit board assembly against becoming detached. These holding means are mounted in a transversely running holding slot in the transverse connecting rail. However, this arrangement has the disadvantage that there are four different elements in order to provide the functions "centering", "ground contact" and "security against falling out". A further disadvantage is that the means provided for the ground contact are not adequate for a protective-ground contact. Furthermore, this adversely affects the function of the coding elements and the coding chambers.
WO 96/42187 discloses a front system for a printed circuit board assembly with active/passive switching. For centering, the end part of the printed circuit board assembly has a guide pin, which is provided to engage in an opposite guide hole. In this arrangement too, an additional screw is provided on the end part to secure the printed circuit board assembly against becoming detached. In the inserted state, this screw can be screwed into a threaded rail, which is mounted in a transverse groove inside the opposite transverse connecting rail. Again, this arrangement has the disadvantage of having multiple parts. Furthermore, there are no additional elements provided to make an electrical protective-ground contact between the front element and the transverse connecting rails.
Finally, WO 97/49270 discloses a mounting rack having plug-in assemblies. The plug-in assemblies have front panels that can be centered. A screw, which passes through the front panel, is provided at one end of such a front panel. Furthermore, guide means, which run in the transverse direction, are mounted in the opposite transverse connecting rail. During insertion of a printed circuit board assembly, which is provided with the front panel, into the corresponding mounting rack, the screw makes contact with the guide means. The guide means have a centering region located at the front and a threaded region located at the rear. In one embodiment, the centering region is formed by a centering strip with equidistant centering holes and the threaded region, which is located behind the centering region, is formed by a threaded strip with equidistant threaded holes. This arrangement has the disadvantage that the parts involved have to accurately fit one another.
Furthermore, there are no additional elements provided for electrical protective-ground contacts between the front panel and the transverse connecting rails.